Ownership, lease and PPA calculator

Customer cash flows for one rooftop under three structures, against the utility bill.

A modelling aid, not financial, tax or legal advice. Nominal USD, year-end flows, pre-tax. Every default is an invented input from the glossary page. The incentive field is a placeholder share of capex, not a credit rate. Residual value, buyout and removal are left out.

Presets:

System size (kW dc, 1 to 100000) Year-1 yield (kWh per kW dc) Output against expectation (%, 10 to 150) Degradation (% per year, 0 to 5) Utility rate in year 1 (USD per kWh) Utility rate escalation (% per year) Term (years, 1 to 30) Host discount rate (%, nominal) Ownership capex (USD per W dc) Ownership O&M in year 1 (USD per kW dc) O&M escalation (% per year) Inverter replacement (USD per W dc) Replacement year (0 = none) Incentive to the owner (% of capex, year 1) PPA price in year 1 (USD per kWh) PPA escalator (% per year) Lease payment (USD per month, year 1) Lease escalator (% per year)

Result (against the utility bill)	Ownership	Lease	PPA
Cash at year 0 (USD)	-	-	-
Net saving in year 1 (USD)	-	-	-
Total net saving over the term (USD)	-	-	-
NPV at the discount rate (USD)	-	-	-
Cumulative cash turns positive (years)	-	-	-

Discount rate where ownership and lease NPV tie	-
Discount rate where ownership and PPA NPV tie	-

Method: ownership saving = bill avoided minus O&M and replacement, plus the placeholder incentive in year 1, with capex at year 0. Lease saving = bill avoided minus twelve monthly payments. PPA saving = bill avoided minus kWh delivered times the PPA price. Under lease and PPA the owner pays O&M (an assumption). Prices rise from year 2. Enter numbers without thousands separators, for example 50000, and use a point or comma for decimals, for example 0.15 or 0,15.